Deposition of 0.5 to 2 Micron Aerosol in the Human Lung

描述（由申请人提供）：沉积量小（小于 2.5微米）颗粒的机制主要是由以下机制控制： 沉降和扩散。我们最近在微重力环境下进行的研究 (MG)环境已经显示出显著程度的增强沉积， 更小的颗粒，与现有的数值模型预测相比， 证词这似乎是由于以前未计算的 对于人肺中流动的不可逆性的影响（有效地 提供增强的扩散）。这种增强的沉积意味着现有的 小颗粒（小于2.5微米）的模型可能低估了接触， 这种增加的暴露发生在敏感的肺泡区域， 肺我们建议通过研究1） 含屏气时扩散对气溶胶扩散的贡献 在气溶胶推注试验中：2）肺中对流混合的增加引起 通过引起肺中流线的复杂混合的流动逆转; 和3）在1G中，通过执行肺内对流混合的增加， 用地面上最小的颗粒进行类似的研究。研究这些 影响，我们建议测量区域沉积和分散的吸入 NASA KC-135微重力飞行器中MG中的0.5和2微米颗粒团 研究飞机上，和0.5微米的颗粒在地面上。通过执行这些 在没有重力的情况下，我们将能够直接研究这些 没有沉降的混杂影响，重力效应 过程这种不受沉积作用影响的直接观测， 这在地球实验室是不可能的。有证据表明，许多肺 开始于小气道或肺泡的疾病， 通过增强扩散的沉积可以提供长期MG 暴露和肺病。这项研究的结果将使现有的模型 局部肺内气溶胶沉积的改善，特别是对于 较小的颗粒（0.5至1微米的颗粒）。此类信息 将提供一个大大改善的基础，评估接触小 在长时间的太空飞行和地球上吸入的颗粒。

DESCRIPTION (provided by the applicant): The deposition of small (less than 2.5Mm) particles in the human lung is governed primarily by the mechanisms of sedimentation and diffusion. Recent studies we performed in the microgravity (MG) environment have shown a significant degree of enhanced deposition of small particles, compared to that predicted by existing numerical models of deposition. It seems likely that this results from the previously unaccounted for effects of the non-reversibility of flows in the human lung (effectively providing enhanced diffusion). Such enhanced deposition means that existing models for small particles (less than 2.5 Mm) probably underestimate exposure, and that this increased exposure occurs in the sensitive alveolar regions of the lung. We propose to investigate enhanced alveolar deposition by studying 1) The contribution of diffusion to aerosol dispersion by inclusion of breathhold in aerosol bolus tests: 2) The increase in convective mixing in the lung caused by flow reversals that induces complex mixing of the streamlines in the lung; and 3) The increase in convective mixing in the lung in 1G by performing similar studies using the smallest particles on the ground. To study these effects, we propose to measure regional deposition and dispersion of inhaled boluses of 0.5 and 2 micron particles in MG in the NASA KC-135 Microgravity research Aircraft, and 0.5 micron particles on the ground. By performing these studies in the absence of gravity we will be able to directly study these effects without the confounding influence of sedimentation, a gravitational process. Such direct observations without the influence of sedimentation are not possible in the terrestrial laboratory. There is evidence for many lung diseases beginning in the small airways or alveoli, and increased alveolar deposition through enhanced diffusion may provide a link between long-term MG exposure and lung disease. The results of this study will allow existing models of regional intrapulmonary aerosol deposition to be improved, especially for the smaller particles (those in the range 0.5 to 1 micron). Such information will provide a much-improved basis for the assessment of exposure to small inhaled particles both in long duration spaceflight and on Earth.